Twenty-six NPC patients underwent serial T1rho-weighted imaging to evaluate the dynamic changes of parotid glands in patients undergoing intensity-modulated radiation therapy. Parotid volumes, T1rho values, mean radiation doses, and xerostomia degrees were recorded. Change rates of T1rho values were correlated with atrophy rates, mean radiation doses and xerostomia degrees. During RT, parotid volume decreased and parotid T1rho values increased significantly. The change rate of T1rho value correlated with the atrophy rate significantly at post-RT. Intra- and interobserver reproducibility of T1rho measurements were excellent. Dynamic changes of radiation-induced parotid damage in NPC patients underwent IMRT could be evaluated by T1rho-weighted imaging.